PROJECT SUMMARY/ABSTRACT Diabetes affects 31 million (12%) U.S. adults, and another 82 million (34%) adults have prediabetes, a precursor to diabetes. The ramifications of diabetes are grave and include cardiovascular disease, disability, and death. While these statistics highlight the importance of diabetes prevention, current approaches have only partial effectiveness. This has created a clear need to identify new primary prevention targets and approaches for diabetes, and depression and depression treatment are strong candidates in this regard. Over 20 years of evidence indicates that depression is an independent, clinically important, robust, biobehaviorally plausible, and modifiable risk factor for diabetes. However, research has yet to determine whether depression treatment can prevent the development of diabetes in people with prediabetes. Given that depression is still receiving limited attention in settings where diabetes prevention occurs (e.g., primary care), there is a large cohort of patients with an underdetected or undertreated diabetes risk factor (depression). This status quo and the strong state of the depression-to-diabetes science create the need for a pilot RCT to evaluate the utility of depression treatment as a new diabetes prevention strategy. Thus, we propose a pilot RCT of 64 primary care patients (50% minority) with a depressive disorder and prediabetes. Patients will be randomized to 6 months of eIMPACT-DM (intervention) or Active Control (comparator). eIMPACT-DM is our modernized collaborative stepped care intervention consisting of (1) computerized and telephonic cognitive-behavioral therapy for depression and (2) select antidepressant medications included in an algorithm optimized for diabetes risk reduction. Our preliminary data establish the feasibility and antidepressive efficacy of eIMPACT-DM. The Active Control consists of depression education, symptom monitoring, and primary care for depression. Our primary aim is to determine the preliminary efficacy of eIMPACT-DM in improving the diabetes risk markers of hemoglobin A1c (primary outcome) and insulin resistance (secondary outcome). Our exploratory aim is to explore whether somatic depressive symptoms ? i.e., hyperphagia (increased appetite/weight) and/or hypersomnia (increased sleep) ? moderate the effect of eIMPACT-DM on diabetes risk markers. A positive pilot trial would pave the way to an R01-level RCT by: (1) generating critical proof-of-concept data (eIMPACT- DM can improve A1c) to support the premise of the definitive trial; (2) providing preliminary effect sizes for eIMPACT-DM on diabetes risk markers to help justify future power analyses; (3) identifying a potentially important moderator of eIMPACT-DM efficacy that may need to be incorporated into the definitive trial. Ultimately, demonstrating that depression treatment reduces diabetes risk would identify a novel target (depression) for diabetes prevention efforts, and it would equip healthcare providers with a new practical, scalable, and disseminable intervention (eIMPACT-DM) to help lower diabetes risk for a large cohort of high- risk patients. These practice changes should translate into reduced diabetes morbidity, mortality, and costs.